Vesicular Gland: Structure, Function & Diseases

A vesicular gland is a paired accessory sex gland of the male. They are located above the prostate gland and open into the urethra along with the vas deferens. The vesicular glands produce an alkaline, fructose-rich secretion for the ejaculate, which mobilizes the sperm and provides them with the necessary energy for their active movement. Approximately 70% of the liquid content in the ejaculate comes from the vesicular glands.

What is the vesicular gland?

The paired vesicular glands (vesicula seminalis), which used to be incorrectly called seminal vesicles, are one of the accessory sex glands of the male. The alkaline secretion synthesized by the vesicular glands is enriched with fructose. About 70% of the fluid contained in the ejaculate comes from the vesicular glands. The secretion serves to create an alkaline environment for the sperm, freeing them from their “acid torpor” and providing the sperm filaments with the necessary energy in the form of fructose for their active movements. The two vesicular glands are located above the prostate between the posterior wall of the urinary bladder and the colon. The secretion produced is usually transported by exocytosis from the cells into the excretory duct, the ductus excretorius, and further into the ureter via the ductus ejaculatorius. The vesicular glands synthesize other substances as well, such as the protein semenogelin, which encloses the sperm in a kind of gel matrix and prevents their premature maturation, which is supposed to occur only in the female genital tract before reaching the female egg.

Anatomy and structure

The vesicular glands have an elongated oval shape and are clustered within themselves. Their length is about 5 cm. The organs each consist of a single, multiply folded duct about 15 cm long with a wide lumen. The excretory ducts at the lower end of the glands unite with the respective vas deferens, the ductus deferens to form the so-called spur duct, the ductus ejaculatorius, which then opens into the urethra. The glandular cells that synthesize the secretion usually transport the secretion outward via exocytosis into the extracellular matrix and onward into the excretory duct. This means that the secretion forms in vesicles within the cells. The vesicles briefly fuse with the cell membrane to subsequently release the secretion. In order for the secretion to be regularly expelled according to sexual stimulation and during ejaculation in the same rhythm and to mix with the other parts of the ejaculate, the epithelial cells adjacent to the lumen have some smooth muscle cells that contract during ejaculation and expel the secretion from the lumina in an impulsive manner.

Function and tasks

The two vesicular glands are classified as accessory sex glands. Their main function is to synthesize certain substances and add them to the ejaculate in the correct proportion during sexual arousal. The secretion produced by the vesicular glands is in the alkaline range and raises the pH of the ejaculate. This releases the sperm formed in the seminiferous tubules from their “acid torpor” and stimulates them to move. To ensure that the sperm do not run out of energy, the fructose contained in the ejaculate is available to them. However, their motility is temporarily artificially slowed down again by a protein to prevent them from maturing too early into fertilizable sperm. The protein causes the sperm to be “packed” in a kind of gel matrix, which is only broken down and dissolved again in the female genital tract. The subsequent maturation process (capacitation) involves a biochemical remodeling process on the cell walls of the sperm filaments. Primarily, a glycoprotein coating on the cell walls is degraded. The process of capacitation is mainly triggered by a specific hormone found in the cervical mucus. The vesicular glands are also responsible for protecting the sperm in the female genital tract from possible immune attack. Therefore, they produce a hormone that attenuates possible immune reactions in the vagina, protecting the sperm on their way to the female egg.

Diseases

In rare cases, malformation or complete absence (aplasia) of one or both vesicular glands occurs during embryonic development, often accompanied by malformation of the vas deferens.The malformations can be traced back to mutations of the CFTR (cystic fibrosis transmembrane conductance regulator). Far more common is an acute or chronic inflammation of the vesicular glands (vesiculitis), which can be caused by infections with bacteria, viruses or fungi. Vesiculitis usually occurs in parallel with inflammation of the prostate. The disease is associated with pain in the lower abdomen, often with nonspecific symptoms such as fever and chills. Blood usually shows up in the ejaculate (semen). Diagnostic imaging techniques such as transrectal ultrasound (TRUS), CT, and MRI are useful for differential diagnosis and exclusion of prostate cancer or TB. The untreated course of vesiculitis can lead to cystitis, an abscess in the vesicular gland, or urosepsis, a bacterial blood poisoning that passes from the genitourinary tract into the blood via the urinary tract. Rare conditions of the vesicular glands include the occurrence of primary or secondary cysts. Primary cysts are congenital and very rare. Much more common are secondary cysts, which are acquired and in many cases associated with benign prostatic hyperplasia. Also very rare are tumors in the vesicular area, which usually occur in younger men of sexually active age.

Typical and common venereal diseases

  • Chlamydia (chlamydial infection).
  • Syphilis
  • Gonorrhea (gonorrhea)
  • Genital warts (HPV) (genital warts)
  • AIDS
  • Ulcus molle (soft chancre)